四川盆地震旦系灯影组储层改造实验与应用

为了提升四川盆地震旦系灯影组储层的改造效果,研究了高温下不同酸液的酸岩反应速率、高闭合压力下不同酸液及不同注入方式下酸蚀裂缝导流能力保持率、酸液穿透实验最低穿透时间、酸蚀裂缝形态特征数值化特征表述及暂堵球转向暂堵效果。在此基础上,提出了适合灯影组储层改造的主体酸液类型,以及适合不同储层类型的主体改造工艺,优化了施工参数。现场试验18口井,平均单井获得井口测试天然气产量45.482×10~4m~3/d。结论认为:①酸岩反应速率影响因素大小为酸液类型温度转速酸液浓度同离子效应,灯影组储层酸化要考虑酸液类型、转速(施工排量)的优化及工艺上降温措施;②采用自生酸+胶凝酸+转向酸注入顺序不但能实现深穿透,而且能同时获得较高的导流能力;③孔洞型储层采用高温胶凝酸改造,非均质性强的储层采用高温转向酸实现均匀改造,岩性致密、裂缝及孔洞均不发育的储层宜采用自生酸与主体酸交替注入造长缝改造;④除了少数裂缝发育储层外,主体工艺应以深度酸压为主;⑤解堵酸化施工排量应不低于3.5 m~3/min;⑥可溶解暂堵球转向酸化工艺技术能够调整酸液在各酸化层的注入量,以实现对非均质储层的均匀改造。

Experimental study and application of stimulation technologies for Sinian Dengying Formation reservoirs in the Sichuan Basin

For improving the stimulation effects of the Sinian Dengying Formation reservoirs in the Sichuan Basin, studies were conducted on the retarding rate of acid-rock reaction speeds of different acidizing fluids at high temperature, the retention rate of flow conductivity of acid-etched fractures under high closure pressure with different acid fluids and injection modes, the minimum breakthrough time in acid fluid breakthrough tests, the numerical characterization of acid-etched fracture morphology, and the diverting plugging effects of ball fracturing. Then, the host types of acid fluids applicable for the Dengying Formation reservoir stimulation were proposed, the principal stimulation technologies for different types of reservoirs were developed and operational parameters were optimized. Field tests were conducted at 18 wells with an average single-well production rate of 45.482×104 m3/d. Finally, the following conclusions are reached. First, the influential factors on acid-rock reaction speeds are ranked as acid fluid type > temperature > rotation speed > acid fluid concentration > common-ion effect. So in the acidizing stimulation of Dongying Formation reservoirs, focus should be on acid fluid types, rotation speed (operational discharge) optimization and cooling measures. Second, not only deep breakthrough can be realized, but also flow conductivity can be higher by using the injection order of self-generating acid + gelled acid + diverting acid. Third, high-temperature gelled acid stimulation is applicable for vuggy reservoirs. For strong-heterogeneity reservoirs high-temperature diverting acid should be adopted to realize uniform stimulation. For tight reservoirs with undeveloped fractures and vuggies, self-generating acid and host acid should be injected alternatively to form long fractures. Fourth, depth acid fracturing should be the principal technology, except for several reservoirs with developed fractures. Fifth, the discharge rate of breakdown acidizing operation should be at least 3.5 m3/min. Sixth, based on the resoluble ball fracturing diverting acidizing technology, the injection rate of acid fluids to each acidified reservoir can be adjusted, so that heterogeneous reservoirs can be stimulated uniformly.